Self-aligned scheme for semiconductor device and method of forming the same

ABSTRACT

In an embodiment, a method includes forming a first conductive feature in a first inter-metal dielectric (IMD) layer; depositing a blocking film over and physically contacting the first conductive feature; depositing a first dielectric layer over and physically contacting the first IMD layer; depositing a second dielectric layer over and physically contacting the first dielectric layer; removing the blocking film; depositing an etch stop layer over any physically contacting the first conductive feature and the second dielectric layer; forming a second IMD layer over the etch stop layer; etching an opening in the second IMD layer and the etch stop layer to expose the first conductive feature; and forming a second conductive feature in the opening.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional of U.S. patent application Ser. No.17/371,416, filed on Jul. 9, 2021, entitled “Self-Aligned Scheme forSemiconductor Device and Method of Forming the Same,” which claims thebenefit of U.S. Provisional Application No. 63/168,389, filed on Mar.31, 2021, which applications are hereby incorporated herein byreference.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (e.g., the number of interconnecteddevices per chip area) has generally increased while geometry size(e.g., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs.

Accompanying the scaling down of devices, manufacturers have begun usingnew and different materials and/or combination of materials tofacilitate the scaling down of devices. Scaling down, alone and incombination with new and different materials, has also led to challengesthat may not have been presented by previous generations at largergeometries.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10A, 10B, 10C, 11A, 11B, 11C, 12A, 12B,and 12C illustrate cross-sectional views of intermediate stages in theformation of interconnect structures of integrated circuits, inaccordance with some embodiments.

FIGS. 13, 14, 15, 16, and 17 illustrate cross-sectional views ofintermediate stages in the formation of interconnect structures ofintegrated circuits, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

According to various embodiments, a semiconductor device (e.g., anintegrated circuit device) may be formed to have first conductivefeatures in a first metallization layer and second conductive featuresin an overlying second metallization layer. When some of the secondconductive features are misaligned over the first conductive features,embodiments described herein are able to prevent or reduce parasiticcapacitance, breakdown pathways, and/or leakage current that mayotherwise be caused by the misalignment. For example, the conductivefeatures, including conductive lines and conductive vias, may formportions of an interconnect structure. The first conductive features areforming in a first insulating layer, and a blocking film is selectivelydeposited over the first conductive features. A first dielectric layer(e.g., a low-k dielectric material) and a second dielectric layer (e.g.,a high-k dielectric material) are selectively deposited (orself-aligned) over the first insulating layer and prevented by theblocking film from depositing over the first conductive features. Theblocking film may then be removed, and an etch stop layer is formed overthe first conductive features and the second dielectric layer. Beforeforming the second conductive features, a second insulating layer isformed and openings are etched through the second insulating layer toexpose the first conductive features. If any of the openings aremisaligned, the second dielectric layer protects the underlying firstinsulating layer from being etched. The second conductive features thatare subsequently formed in the misaligned openings will physicallycontact the underlying first conductive features while also having anoverbite portion that hangs over the second dielectric layer. Becausethe overbite portion of those second conductive features may be closerto other nearby conductive features, presence of the first dielectriclayer ensures that parasitic capacitance is prevented or reduced due tothe first dielectric layer being a low-k dielectric material. Forexample, parasitic capacitance is prevented or reduced between anynearby conductive features—which may be ones of the second conductivefeatures (e.g., conductive lines and/or conductive vias) and/or ones ofthe first conductive features—whether formed with correct alignment ormisaligned. As a result of the disclosed embodiments, the semiconductordevice may be manufactured with increased yield and function withgreater reliability.

FIGS. 1 through 17 illustrate cross-sectional views of intermediatestages in the formation of interconnect structures comprising conductivefeatures of an integrated circuit device, in accordance with someembodiments. FIGS. 1 through 8 may illustrate formation of firstconductive features in a first metallization layer of an interconnectstructure using a single damascene process. FIGS. 9 through 12C mayillustrate formation of second conductive features in a secondmetallization layer (e.g., including conductive lines and/or conductivevias) of an interconnect structure using a single or dual damasceneprocess. FIGS. 13 through 17 may illustrate other embodiments in theformation of first and second conductive features of an interconnectstructure using a single or dual damascene process.

FIG. 1 illustrates a cross-sectional view of a semiconductor structureon a wafer too comprising a substrate 50 (e.g., a semiconductorsubstrate) in which various electronic devices may be formed over thesubstrate 50, in accordance with some embodiments. In subsequentfigures, a multilevel interconnect system (e.g., a front-sideinterconnect structure) may be formed over the various electronicdevices and the substrate 50. Generally, as will be discussed in greaterdetail below, FIG. 1 illustrates a Fin field effect transistor (FinFET)device 60 formed on a substrate 50, with multiple metallization layersformed thereover in later figures. Planar transistors, gate-all-around(GAA) transistors, and other types of devices are within thecontemplated scope of this disclosure, however.

Generally, the substrate 50 illustrated in FIG. 1 may comprise a bulksemiconductor substrate or a silicon-on-insulator (SOI) substrate. AnSOI substrate includes an insulator layer below a thin semiconductorlayer that is the active layer of the SOI substrate. The semiconductorof the active layer and the bulk semiconductor generally comprise thecrystalline semiconductor material silicon, but may include one or moreother semiconductor materials such as germanium, silicon-germaniumalloys, compound semiconductors (e.g., GaAs, AlAs, InAs, GaN, AlN, andthe like), or their alloys (e.g., Ga_(x)Al_(1-x)As, Ga_(x)Al_(1-x)N,In_(x)Ga_(1-x)As and the like), oxide semiconductors (e.g., ZnO, SnO₂,TiO₂, Ga₂O₃, and the like) or combinations thereof. The semiconductormaterials may be doped or undoped. Other substrates that may be usedinclude multilayered substrates, gradient substrates, or hybridorientation substrates.

The FinFET device 60 illustrated in FIG. 1 is a three-dimensionalmetal-on-semiconductor field effect transistor (MOSFET) structure formedin fin-like strips of semiconductor protrusions referred to as fins 58.The cross-section shown in FIG. 1 is taken along a longitudinal axis ofthe fin in a direction parallel to the direction of the current flowbetween the source and drain regions 54. The fin 58 may be formed bypatterning the substrate using photolithography and etching techniques.For example, a spacer image transfer (SIT) patterning technique may beused. In this method a sacrificial layer is formed over a substrate andpatterned to form mandrels using suitable photolithography and etchprocesses. Spacers are formed alongside the mandrels using aself-aligned process. The sacrificial layer is then removed by anappropriate selective etch process. Each remaining spacer may then beused as a hard mask to pattern the respective fin 58 by etching a trenchinto the substrate 50 using, for example, reactive ion etching (RIE).FIG. 1 illustrates a single fin 58, although the substrate 50 maycomprise any number of fins.

Shallow trench isolation (STI) regions 62 formed along opposingsidewalls of the fin 58 are illustrated in FIG. 1 . STI regions 62 maybe formed by depositing one or more dielectric materials (e.g., siliconoxide) to completely fill the trenches around the fins and thenrecessing the top surface of the dielectric materials. The dielectricmaterials of the STI regions 62 may be deposited using a high densityplasma chemical vapor deposition (HDP-CVD), a low-pressure CVD (LPCVD),sub-atmospheric CVD (SACVD), a flowable CVD (FCVD), spin-on, and/or thelike, or a combination thereof. After the deposition, an anneal processor a curing process may be performed. In some cases, the STI regions 62may include a liner such as, for example, a thermal oxide liner grown byoxidizing the silicon surface. The recess process may use, for example,a planarization process (e.g., a chemical mechanical polish (CMP))followed by a selective etch process (e.g., a wet etch, or dry etch, ora combination thereof) that may recess the top surface of the dielectricmaterials in the STI region 62 such that an upper portion of the fins 58protrudes from surrounding insulating STI regions 62. In some cases, thepatterned hard mask used to form the fins 58 may also be removed by theplanarization process.

In some embodiments, the gate structure 68 of the FinFET device 60illustrated in FIG. 1 may be a high-k, metal gate (HKMG) gate structurethat may be formed using a gate-last process flow. In a gate lastprocess flow, a sacrificial dummy gate structure (not shown) is formedover the fin 58 after forming the STI regions 62. The dummy gatestructure may comprise a dummy gate dielectric, a dummy gate electrode,and a hard mask. First, a dummy gate dielectric material (e.g., siliconoxide, silicon nitride, silicon oxynitride, or the like) may bedeposited. Next, a dummy gate material (e.g., amorphous silicon,polycrystalline silicon, or the like) may be deposited over the dummygate dielectric and then planarized (e.g., by CMP). A hard mask layer(e.g., silicon nitride, silicon carbide, or the like) may then be formedover the dummy gate material. The dummy gate structure is then formed bypatterning the hard mask and transferring that pattern to the dummy gatedielectric and dummy gate material using suitable photolithography andetching techniques. The dummy gate structure may extend along multiplesides of the protruding fins 58 and extend between the fins 58 over thesurface of the STI regions 62. As described in greater detail below, thedummy gate structure may be replaced by the gate structure 68 asillustrated in FIG. 1 . The gate structure 68 illustrated in the rightside in FIG. 1 (seen on the top of fin 58) is an example of an activegate structure which extends, e.g., along sidewalls of and over theportion of fin 58 protruding above the STI region 62. The gate structure68 in the left side in FIG. 1 is an example gate structure extendingover the STI region 62, such as between adjacent fins 58. The materialsused to form the dummy gate structure and hard mask may be depositedusing any suitable method such as CVD, plasma-enhanced CVD (PECVD),atomic layer deposition (ALD), plasma-enhanced ALD (PEALD) or the like,or by thermal oxidation of the semiconductor surface, or combinationsthereof.

Source and drain regions 54 and spacers 72 of FinFET 6 o, illustrated inFIG. 1 , are formed, for example, self-aligned to the dummy gatestructures. Spacers 72 may be formed by deposition and anisotropic etchof a spacer dielectric layer performed after the dummy gate patterningis complete. The spacer dielectric layer may include one or moredielectrics, such as silicon oxide, silicon nitride, silicon oxynitride,silicon carbide, silicon carbonitride, the like, or a combinationthereof. The anisotropic etch process removes the spacer dielectriclayer from over the top of the dummy gate structures leaving the spacers72 along the sidewalls of the dummy gate structures extending laterallyonto a portion of the surface of the fin 58 (as illustrated in the rightside of FIG. 1 ) or the surface of the STI region 62 (as illustrated inthe left side of FIG. 1 ).

The source and drain regions 54 are semiconductor regions in contactwith the fin 58. In some embodiments, the source and drain regions 54may comprise heavily-doped regions and relatively lightly-doped drain(LDD) extensions. Generally, the heavily-doped regions are spaced awayfrom the dummy gate structures using the spacers 72, whereas the LDDregions may be formed prior to forming spacers 72 and, hence, extendunder the spacers 72 and, in some embodiments, extend further into aportion of the semiconductor below the dummy gate structure. The LDDregions may be formed, for example, by implanting dopants (e.g., As, P,B, In, or the like) using an ion implantation process.

The source and drain regions 54 may comprise an epitaxially grownregion. For example, after forming the LDD regions, the spacers 72 maybe formed and, subsequently, the heavily-doped regions of the source anddrain regions 54 may be formed self-aligned to the spacers 72. Inparticular, the heavily-doped drain regions may be formed by firstetching the fins to form recesses, and then depositing a crystallinesemiconductor material in the recess by a selective epitaxial growth(SEG) process that may fill the recess and, typically, extend beyond andabove the original surface of the fin to form a raised source-drainstructure, as illustrated in FIG. 1 . The crystalline semiconductormaterial may be elemental (e.g., Si, or Ge, or the like), or an alloy(e.g., Si_(1-x)C_(x), or Si_(1-x)Ge_(x), Si_(1-x-y)Ge_(x)C_(y), or thelike). The SEG process may use any suitable epitaxial growth method,such as e.g., vapor/solid/liquid phase epitaxy (VPE, SPE, LPE), ormetal-organic CVD (MOCVD), or molecular beam epitaxy (MBE), or the like.A high dose (e.g., from about 10¹⁴ cm⁻² to 10¹⁶ cm⁻²) of dopants may beintroduced into the heavily-doped regions of the source and drainregions 54 either in situ during SEG, by an ion implantation processperformed after the SEG, or by a combination thereof. The source anddrain regions 54 may be formed by other processes, such as ionimplantation of dopants, and the like.

Still referring to FIG. 1 , a first interlayer dielectric (ILD) layer 76is deposited over the structure. In some embodiments, a contact etchstop layer (CESL) (not shown) of a suitable dielectric (e.g., siliconnitride, silicon carbide, or the like, or a combination thereof) may bedeposited prior to depositing the ILD material. A planarization process(e.g., CMP) may be performed to remove excess ILD material and anyremaining hard mask material from over the dummy gates to form a topsurface wherein the top surface of the dummy gate material is exposedand may be substantially coplanar with the top surface of the first ILDlayer 76.

The gate structures 68, illustrated in FIG. 1 , may then be formed byfirst removing the dummy gate structures using one or more etchingtechniques, thereby creating recesses between respective spacers 72.Next, a replacement gate dielectric layer 66 comprising one or moredielectrics, followed by a replacement conductive gate layer 64comprising one or more conductive materials, may be deposited tocompletely fill the recesses. The gate dielectric layer 66 includes, forexample, a high dielectric constant (high-k) material such as oxidesand/or silicates of metals (e.g., oxides and/or silicates of Hf, Al, Zr,La, Mg, Ba, Ti, and other metals), silicon nitride, silicon oxide, andthe like, combinations thereof, or multilayers thereof. In someembodiments, the conductive gate layer 64 may be a multilayered metalgate stack comprising a barrier layer, a work function layer, and agate-fill layer formed successively on top of gate dielectric layer 66.Example materials for a barrier layer include TiN, TaN, Ti, Ta, TiSiN,TaSiN, or the like, or a multilayered combination thereof. A workfunction layer may include TiN, TaN, Ru, Mo, Al, for a p-type FET, andTi, Ag, TaAl, TaAlC, TiAlN, TaC, TaCN, TaSiN, Mn, Zr, for an n-type FET.Other suitable work function materials, or combinations, or multilayersthereof may be used. The gate-fill layer which fills the remainder ofthe recess may comprise metals such as Cu, Al, W, Co, Ru, or the like,or combinations thereof, or multi-layers thereof. The materials used informing the gate structure may be deposited by any suitable method,e.g., CVD, PECVD, physical vapor deposition (PVD), ALD, PEALD,electrochemical plating (ECP), electroless plating and/or the like.Excess portions of the gate structure layers 64 and 66 may be removedfrom over the top surface of first ILD layer 76 using, for example, aCMP process. The resulting structure, as illustrated in FIG. 1 , mayhave a substantially coplanar surface comprising an exposed top surfaceof the first ILD layer 76, the spacers 72, and remaining portions of thegate layers (e.g., the gate structure layers 64 and 66) inlaid betweenrespective spacers 72.

A second ILD layer 78 may be deposited over the first ILD layer 76, asillustrated in FIG. 1 . In some embodiments, the insulating materials toform the first ILD layer 76 and the second ILD layer 78 may comprisesilicon oxide, phosphosilicate glass (PSG), borosilicate glass (BSG),boron-doped phosphosilicate glass (BPSG), undoped silicate glass (USG),a low dielectric constant (low-k) material such as, fluorosilicate glass(FSG), silicon oxycarbide (SiOCH), carbon-doped oxide (CDO), flowableoxide, or porous oxides (e.g., xerogels/aerogels), or the like, or acombination thereof. The dielectric materials used to form the first ILDlayer 76 and the second ILD layer 78 may be deposited using any suitablemethod, such as CVD, PVD, ALD, PEALD, PECVD, SACVD, FCVD, spin-on,and/or the like, or a combination thereof. In some embodiments, one ormore etch stop layers (not specifically illustrated) are also formedover the structure above and/or below the illustrated ILD layers.

As illustrated in FIG. 1 , electrodes of electronic devices formed inthe substrate 50 may be electrically connected to subsequently formedconductive features of a first metallization level using conductiveconnectors (e.g., contact plugs 74) formed through the interveningdielectric layers. In the example illustrated in FIG. 1 , the contactplugs 74 make electrical connections to the source and drain regions 54of the FinFET 60. The contact plugs 74 to gate electrodes are typicallyformed over STI regions 62. A separate gate electrode 64 (shown in theleft in FIG. 1 ) illustrates such contacts. The contact plugs 74 may beformed using photolithography techniques. For example, a patterned maskmay be formed over the second ILD layer 78 and used to etch openingsthat extend through the second ILD layer 78 to expose a portion of thegate electrodes 64 over the STI regions 62, as well as to etch openingsover the fins 58 that extend further, through the first ILD layer 76 andthe CESL (not shown) liner below first ILD layer 76 to expose portionsof the source and drain regions 54. In some embodiments, an anisotropicdry etch process may be used wherein the etching is performed in twosuccessive steps. The etchants used in the first step of the etchprocess have a higher etch rate for the materials of the first andsecond ILD layers 76 and 78 relative to the etch rate for the materialsused in the conductive gate layer 64 and the CESL, which may be liningthe top surface of the heavily-doped regions of the source and drainregions 54. Once the first step of the etch process exposes the CESL,the second step of the etch process may be performed wherein theetchants may be switched to selectively remove the CESL. While the twoILD layers (e.g., the first ILD layer 76 and the second ILD layer 78)are illustrated, embodiments having only a single ILD layer, or havingthree or more ILD layers, are within the contemplated scope of thisdisclosure.

In some embodiments, a conductive liner may be formed in the openings inthe first ILD layer 76 and the second ILD layer 78. Subsequently, theopenings are filled with a conductive fill material. The liner comprisesbarrier metals used to reduce out-diffusion of conductive materials fromthe contact plugs 74 into the surrounding dielectric materials. In someembodiments, the liner may comprise two barrier metal layers. The firstbarrier metal comes in contact with the semiconductor material in thesource and drain regions 54 and may be subsequently chemically reactedwith the heavily-doped region in the source and drain regions 54 to forma low resistance ohmic contact, after which the unreacted metal may beremoved. For example, if the heavily-doped region in the source anddrain regions 54 is silicon or silicon-germanium alloy semiconductor,then the first barrier metal may comprise Ti, Ni, Pt, Co, other suitablemetals, or their alloys. The second barrier metal layer of theconductive liner may additionally include other metals (e.g., TiN, TaN,Ta, or other suitable metals, or their alloys). The conductive fillmaterial (e.g., W, Al, Cu, Ru, Ni, Co, alloys of these, the like, or anycombination thereof) may be deposited over the conductive liner layer tofill the contact openings, using any acceptable deposition technique(e.g., CVD, ALD, PEALD, PECVD, PVD, ECP, electroless plating, the like,or any combination thereof). Next, a planarization process (e.g., CMP)may be used to remove excess portions of all the conductive materialsfrom over the surface of the second ILD layer 78. The resultingconductive plugs extend into the first and second ILD layers 76 and 78and constitute the contact plugs 74 making physical and electricalconnections to the electrodes of electronic devices, such as the FinFETdevice 60 (e.g., a tri-gate FinFET), as illustrated in FIG. 1 . In thisexample, contacts to electrodes over the STI region 62 and to electrodesover the fins 58 are formed simultaneously using the same processingsteps. However, in other embodiments these two types of contacts may beformed separately.

In FIGS. 2 through 18C, a front-side interconnect structure 80 is formedover the second ILD layer 78. The front-side interconnect structure 80may be electrically connected to the contact plugs 74. In FIGS. 2-12 ,first conductive features 120 of the front-side interconnect structure80 are formed in an inter-metal dielectric (IMD) layer 110. In FIGS.13-18C, second conductive features 220 of the front-side interconnectstructure 80 are formed in an IMD layer 210 over and electricallyconnected to the first conductive features 120.

In FIG. 2 , an etch stop layer 108 is formed over the FinFETs 60 andother electronic devices, the second ILD layer 78, and the contact plugs74, and the IMD layer 110 is formed over the etch stop layer 108. Theetch stop layer 108 may be formed from silicon carbide, silicon nitride,silicon oxynitride, silicon carbonitride, aluminum nitride, aluminumoxide, the like, or combinations thereof. The etch stop layer 108 may beformed by CVD, PVD, ALD, a spin-on-dielectric process, the like, or acombination thereof. The IMD layer 110 may be a layer formed from alow-k dielectric material, for example, having a k-value lower thanabout 3.9. The IMD layer 110 may be a layer formed from an extra-low-k(ELK) dielectric material having a k-value of less than 2.5. In someembodiments, the IMD layer 110 may be formed from an oxygen-containingand/or carbon containing low-k dielectric material, such as siliconoxide, Hydrogen SilsesQuioxane (HSQ), MethylSilsesQuioxane (MSQ), or thelike. The material of the etch stop layer 108 has a high etchselectivity with the IMD layer 110 (e.g., different etch selectivitiessuch that the faster of these etch rates may be more than 5 times fasterthan the slower of these etch rates), and hence the etch stop layer 108may be used to stop the etching of the IMD layer 110 in subsequentprocessing steps.

In some embodiments, the IMD layer 110 is formed from a porous materialsuch as SiOCN, SiCN, SiOC, SiOCH, or the like and may be formed byinitially forming a precursor layer over the etch stop layer 108. Theprecursor layer may include both a matrix material and a porogeninterspersed within the matrix material, or may alternatively includethe matrix material without the porogen. In some embodiments theprecursor layer may be formed, for example, by co-depositing the matrixand the porogen using a process such as PECVD where the matrix materialis deposited at the same time as the porogen, thereby forming theprecursor layer with the matrix material and the porogen mixed together.However, as one of ordinary skill in the art will recognize,co-deposition using a simultaneous PECVD process is not the only processthat may be used to form the precursor layer. Any suitable process, suchas premixing the matrix material and the porogen material as a liquidand then spin-coating the mixture onto the etch stop layer 108, may alsobe utilized.

In FIG. 3 , the first conductive features 120 are formed in the IMDlayer 110. Openings are formed in the IMD layer 110 using aphotolithography process. For example, a buffer layer and a mask layermay be formed over the IMD layer 110, patterned using a photoresist, andetched to form initial openings. The openings may then be extendedthrough the IMD layer 110 using acceptable etching techniques, such asan isotropic or an anisotropic process. For example, an anisotropic dryetch process may include a reaction gas that selectively etches the IMDlayer 110 without significantly etching the mask layer. The etchingprocess is performed until the openings expose the etch stop layer 108,and then portions of the etch stop layer 108 in the openings areremoved, such as using an anisotropic wet or dry etch process, to exposethe underlying target contact plugs 74.

The first conductive features 120 may be formed in the openings bydepositing a liner layer 140 along walls of the openings, a conductivefill material 150 in the openings, and a capping layer 160 over theconductive fill material 150. Although not specifically illustrated, theliner layer 140 may comprise a plurality of layers, including a barrierand one or more liners. For example, the barrier of the liner layer 140is formed on the exposed surface of wafer too and in the openings byPVD, ALD, the like, or a combination thereof. The barrier may comprise ametal, such as titanium, tantalum, tantalum nitride, the like, or acombination thereof. In addition, each of the liners is formed on thebarrier and in the openings by CVD, PVD, ALD, the like, or a combinationthereof. Each of the liners may comprise cobalt, ruthenium, molybdenum,rhodium, the like, or a combination thereof. In accordance with someembodiments, after forming the liners, a liner treatment, such as ahydrogen soak treatment and/or a hydrogen plasma treatment, may beperformed to convert the liners into a combined liner.

After forming the liner layer 140, the conductive fill material 150 isdeposited to fill a remainder of the openings. Excess conductivematerial may also be formed along a top surface of the liner layer 140and over the IMD layer 110. The conductive fill material 150 may be ametallic material including a metal or a metal alloy such as copper,silver, gold, tungsten, cobalt, aluminum, manganese, or alloys thereof.In some embodiments, the formation of the conductive fill material 150includes depositing a thin seed layer (not shown), which may includecopper or a copper alloy, and filling the rest of the openings usingCVD, PVD, ALD, ECP, such as high voltage ECP, or electroless plating.

A planarization process may be performed to remove excess of theconductive fill material 150 and the liner layer 140. In addition, theplanarization process may remove remaining portions of the mask layerand the buffer layer, thereby exposing a top surface of the IMD layer110. The planarization process may be a grinding or a CMP, and may beperformed such that the top surfaces of the conductive fill materialiso, the liner layer 140, and the IMD layer 110 are level (withinprocess variations).

After the planarization process, the capping layer 160 is deposited overthe IMD layer 110, the liner layer 140, and the conductive fill material150 using CVD, PECVD, PVD, ALD, PEALD, ECP, electroless plating, and/orthe like. The capping layer 160 may comprise cobalt, ruthenium, thelike, or a combination thereof. The capping layer 160 providesprotection from oxidation of underlying portions of the first conductivefeatures 120, such as the conductive fill material iso. After depositingthe material for the capping layer 160, excess portions may be removedwith any suitable method, such as using lithography. For example, aphotoresist may be formed over the material of the capping layer 160 andpatterned to expose portions of the material of the capping layer 160that are not directly over the liner layer 140 and the conductive fillmaterial 150. The exposed portions may then be removed by etching or anysuitable method, and the photoresist may then be removed by any suitablemethod. In some embodiments, the capping layer 160 is selectivelydeposited over the conductive fill material 150 or over both theconductive fill material 150 and the liner layer 140. In someembodiments, small amounts of the capping layer 160 may also depositover the IMD layer 110. The capping layer 160 may be deposited using anyof the techniques identified with respect to the layers of the linerlayer 140 or the conductive fill material iso. The capping layer 160 maythen be patterned to remove portions such as the small amounts depositedover the IMD layer 110. The capping layer 160 may have a thickness ofbetween about 5 Å and about 40 Å.

It should be noted that although each of the first conductive features120 is illustrated as being located in the same cross-section, some ofthe first conductive features 120 may be located in differentcross-sections. However, in some embodiments, neighboring or adjacentones of the first conductive features 120 may be in the samecross-section and have a distance D₁ from one another.

In FIG. 4 , a blocking film formed over and aligned with the firstconductive features 120 (e.g., the capping layer 160). In accordancewith some embodiments, the blocking film 170 is selectively depositedover the capping layer 160, while the exposed surface of the IMD layer110 remains substantially free of the blocking film 170. The blockingfilm 170 may comprise a self-assembling monolayer (SAM) materialincluding hydrophilic head and hydrophobic tail groups. For example, thehydrophilic head groups of the blocking film 170 may comprise phosphategroups and/or high-nitrogen (hi-N) groups and may be inorganic. Inaddition, the hydrophobic tail groups of the blocking film 170 may beorganic and comprise one or more carbon chains.

When deposited, the blocking film 170 may comprise an organic layer, aself-cross-link layer, a self-adhesion layer, other suitable layer, orcombinations thereof. In some embodiments, the blocking film 170 iscoated on the capping layer 160 by a chemical adsorption process, suchthat the blocking film 170 adsorbs only to the metal surface of thecapping layer 160, while the IMD layer 110 remains substantially free ofthe blocking film 170 due to having a different polarity. In particular,the hydrophilic head groups adsorb to the surface of the capping layer160 while the hydrophobic tail groups will tend to orient to form anexposed top surface of the blocking film 170 (e.g., distal or oppositefrom the capping layer 160). A thickness of the blocking film 170 may bemodulated, such as being increased between subsequently formed higherlevel conductive features of the front-side interconnect structure 80.For example, the thickness of the blocking film 170 may be between aboutto A and about too A.

In FIG. 5 , a first dielectric layer 174 of a multilayer dielectric isformed over and aligned with the IMD layer 110, and may further beformed adjacent to sidewalls of the capping layer 160 and the blockingfilm 170. In accordance with some embodiments, the first dielectriclayer 174 is formed through selective deposition using ALD, CVD, or thelike, over the IMD layer 110, while the exposed top surface of theblocking film 170 remains substantially free of the first dielectriclayer 174. For example, the first dielectric layer 174 may comprise alow-k material, such as silicon oxide (SiO_(x)), silicon oxycarbide(SiO_(x)C_(y)), silicon carbonitride (SiC_(y)N_(z)), siliconoxycarbonitride (SiO_(x)C_(y)N_(z)), boronitride, aluminum boronitride,the like, or combinations thereof. In some embodiments, the firstdielectric layer 174 may have a dielectric constant of between about 2.6and about 5.

The first dielectric layer 174, having a compatible polarity with theIMD layer 110, will self-align over the IMD layer 110 while tending toavoid the blocking film 170 (e.g., the hydrophobic tail groups) alongthe exposed top surface of the blocking film 170. Being formed of alow-k material, the first dielectric layer 174 reduces or preventsparasitic capacitance between subsequently formed conductive features(e.g., second conductive features 220 discussed below) and nearby firstconductive features 120. In particular, parasitic capacitance is reducedor prevented between all conductive features (e.g., the first conductivefeatures 120 and the second conductive features 220/220M) whether one orboth have been aligned correctly or misaligned. The reduction ofparasitic capacitance may be particularly advantageous when thosesubsequently formed conductive features are misaligned over thecorresponding first conductive features 120, thereby resulting inseparation distances less than the distance D₁, as discussed in greaterdetail below. Similarly as with the blocking film 170, a thickness ofthe first dielectric layer 174 may be modulated, such as being increasedbetween subsequently formed higher level conductive features of thefront-side interconnect structure 80. For example, the thickness of thefirst dielectric layer 174 may be between about 10 Å and about 50 Å.

In FIG. 6 , a second dielectric layer 178 of the multilayer dielectricis formed over and aligned with the first dielectric layer 174, and mayfurther be adjacent to sidewalls of the blocking film 170. In accordancewith some embodiments, the second dielectric layer 178 is formed throughselective deposition using ALD, CVD, or the like, over the firstdielectric layer 174, while the exposed top surface of the blocking film170 remains substantially free of the second dielectric layer 178. Forexample, the second dielectric layer 178 may comprise a high-k material,such as a metal oxide or metal nitride, including aluminum oxide(Al₂O₃), aluminum nitride (Al₂N₃), aluminum oxynitride (AlON), yttriumoxide (Y₂O₃), silicon carbide, silicon carbonitride, siliconoxycarbonitride, the like, or combinations thereof. In some embodiments,the second dielectric layer 178 may have a dielectric constant ofgreater than 5, such as between about 7 and 14.

The second dielectric layer 178, having a compatible polarity with thefirst dielectric layer 174, will self-align over the first dielectriclayer 174 while tending to avoid the blocking film 170 (e.g., thehydrophobic tail groups) along the exposed top surface of the blockingfilm 170. The material of the second dielectric layer 178 is chosen ashaving a high etch selectivity with a subsequently formed etch stoplayer 208. Having the high etch selectivity allows the second dielectriclayer 178 to remain intact when openings are later formed in the etchstop layer 208. The high etch selectivity may be particularlyadvantageous when those openings are misaligned over the IMD layer 110,as discussed in greater detail below. Similarly as with the blockingfilm 170 and the first dielectric layer 174, a thickness of the seconddielectric layer 178 may be modulated, such as being increased betweensubsequently formed higher level conductive features of the front-sideinterconnect structure 80 or, in other embodiments, the first dielectriclayer 174 may be increased for the higher level conductive featureswhile the second dielectric layer 178 remains the same due to its higherdielectric constant. For example, the thickness of the second dielectriclayer 178 may be between about 10 Å and about 40 Å.

In FIG. 7 , the blocking film 170 is removed, thereby exposing thecapping layer 160. In some embodiments, the blocking film 170 is removedby a hydrogen treatment. For example, a reacting gas comprising H₂ maybe flowed over the structure at pressures of between about 1 Torr andabout 3 Torr and at temperatures of between about 250° C. and about 400°C. The hydrophilic head groups (e.g., the inorganic material) of theblocking film 170 react with the H₂ gas, and the blocking film 170 isremoved from the surface of the capping layer 160. In other embodiments,the blocking film 170 is removed by a nitrogen treatment. For example, areacting gas comprising N₂, NH₃, or a combination thereof is flowed overthe structure treatment at pressures of between about 1 Torr and about 3Torr and at temperatures of about 250° C. to about 400° C. Thehydrophilic tail groups (e.g. the inorganic material) of the blockingfilm 170 react with the nitrogen-containing gas, and the blocking film170 is removed from the surface of the capping layer 160. Asillustrated, after removing the blocking film 170, a top surface of thesecond dielectric layer 178 may be higher than the top surface of thecapping layer 160. In some embodiments, a top surface of the firstdielectric layer 174 may also be higher than the top surface of thecapping layer 160.

In FIG. 8 , an etch stop layer 208 is formed over the first conductivefeatures 120 and the second dielectric layer 178. The etch stop layer208 may be conformally deposited and formed of similar materials (e.g.,silicon carbide, silicon nitride, silicon oxynitride, siliconcarbonitride, aluminum oxide (AlO_(x)), aluminum nitride, or the like)and by a similar process (e.g., using ALD, CVD, or the like) asdescribed above in connection with the etch stop layer 108. As discussedabove, the etch stop layer 208 may have a high etch selectivity with thesecond dielectric layer 178 (e.g., an etch rate of the etch stop layer208 may be up to about 10 times faster than an etch rate of the seconddielectric layer 178). In some embodiments, the etch stop layer 208 mayhave a low etch selectivity with the first dielectric layer 174 (e.g.,having similar etch rates). The low etch selectivity may be due to theetch stop layer 208 and the first dielectric layer 174 comprisingsimilar materials. The etch stop layer 208 may be formed to a thicknessof between about 5 Å and about 150 Å.

In FIG. 9 , an IMD layer 210 and a film stack (e.g., a buffer layer 214,and a mask layer 216) are formed over the etch stop layer 208. The IMDlayer 210 may be formed of similar materials and by a similar process asdescribed above in connection with the IMD layer 110. In addition, thebuffer layer 214 and the mask layer 216 may be formed of similarmaterials and by similar processes as described above in connection withthe buffer layer and the mask layer, respectively, formed over the IMDlayer 110. The material of the etch stop layer 208 has a high etchselectivity with the IMD layer 210, and hence the etch stop layer 208may be used to stop the etching of the IMD layer 210 in subsequentprocessing steps.

In some embodiments, the film stack includes more than one buffer layer214 and mask layer 216, which may be formed in alternating fashion. Thebuffer layer 214 may be formed from a dielectric, such as silicon oxide,and may be formed by CVD, PVD, ALD, a spin-on-dielectric process, or thelike. The mask layer 216 may be formed from a material that includes ametal, such as titanium nitride, titanium, tantalum nitride, tantalum,or the like, and may be formed by PVD, Radio Frequency PVD (RFPVD), ALD,or the like. The buffer layer 214 and the mask layer 216 may be formedof similar materials and by similar processes as used with the bufferlayer and the mask layer formed over the IMD layer 110 as discussedabove.

In FIGS. 10A through 10C, openings or trenches 230 are formed in themask layer 216, and the openings 230 are extended through the bufferlayer 214, the IMD layer 210, and the etch stop layer 208. For example,a pattern is formed on the mask layer 216. The mask layer 216 is thenused as an etching mask, where the pattern of the mask layer 216 is usedto etch the buffer layer 214 and the IMD layer 110. The buffer layer 214provides stress reduction between the IMD layer 110 and the mask layer216.

The openings 230 may be formed and extended by the acceptable etchingtechniques and etchants described above in connection with openings 130,such as using an isotropic etch, an anisotropic etch, or a combinationthereof. The openings 230 expose the underlying first conductivefeatures 120 (e.g., the capping layer 160). The etch stop layer 108 maythen be removed using an isotropic wet etch or an anisotropic wet or dryetch that is selective to the material of the etch stop layer 108. Forexample, using an anisotropic wet etch, the etchant reactants maycomprise H₂O₂, HF, ammonium fluoride (NH₄F), ozone deionized water(DI-O₃), the like, or combinations thereof. The etching process used toremove the etch stop layer 108 may be similar or different from theetching processes used to form the openings 130 (e.g., differentetchants, etching techniques, and/or process parameters may be used).

The openings 230 may be patterned using a dual damascene process, asillustrated, or using a single damascene process. For example, in a dualdamascene process, upper portions of the openings 230 will housemetallization lines of the second conductive features 220, and lowerportions of the openings 230 will house conductive vias of the secondconductive features 220 to electrically connect the second conductivefeatures 220 with the underlying first conductive features 120. Notethat although each of the openings 230 is illustrated as being locatedin the same cross-section, some of the openings 230 may be located indifferent cross-sections.

As further illustrated, in accordance with some embodiments, some of theopenings 230 may be misaligned openings 230M, which overhang (or aremisaligned with) an underlying first conductive feature 120. As aresult, a bulk of a lower portions of the misaligned openings 230M maybe directly over the first conductive features 120, while a minority maybe directly over the second dielectric layer 178, the first dielectriclayer 174, and the IMD layer 110. When the misaligned opening 230Mextends through the etch stop layer 208 and reaches a top surface of thesecond dielectric layer 178, the second dielectric layer 178 remainssubstantially unetched due to having a high etch selectivity with theetch stop layer 208, which the etchants are selected to etch. As aresult, the second dielectric layer 178 protects the IMD layer 110 frombeing etched under the misaligned openings 230M. In addition, the seconddielectric layer 178 may also substantially protect the first dielectriclayer 174 (which may have a low etch selectivity with the etch stoplayer 208) from being etched, thereby allowing the first dielectriclayer 174 to assist in protecting the IMD layer 110.

In FIGS. 10B and 10C, zoomed-in views of region 234 (see FIG. 10A)illustrate varying shapes of the lower portions of one of the alignedopenings 230 and one of the misaligned openings 230M. The selection ofetchants, etching methods (e.g., isotropic or anisotropic), andmaterials of the first dielectric layer 174, the second dielectric layer178, and the etch stop layer 208 may affect the shapes of the openings230. In addition, presence of the first dielectric layer 174 and thesecond dielectric layer 178 reduce distances between one of the firstconductive features 120 and the misaligned opening 230M (including asubsequently formed misaligned second conductive feature 220M, asdiscussed below). Reducing these distances helps to prevent or reduceparasitic capacitance that may otherwise occur between the firstconductive feature 120 and the misaligned second conductive feature220M. Further, presence of the first dielectric layer 174 (e.g., a low-kdielectric layer) prevents or reduces any parasitic capacitance that mayotherwise occur.

Referring to FIG. 10B, in some embodiments, the openings 230 may beformed using an anisotropic dry etch process, and the lower portion ofthe misaligned opening 230M may expose a first width W₁ of the topsurface of the second dielectric layer 178. As illustrated, the highetch selectivity between the second dielectric layer 178 and the etchstop layer 208 results in the etchant substantially stopping at thesecond dielectric layer 178. In addition, the second dielectric layer178 protects the first dielectric layer 174 from being etched. Forexample, the first width W₁ may be between about 0 Å and about 50 Å.

Referring to FIG. 10C, in other embodiments, the openings 230 may beformed using an isotropic or an anisotropic wet etch process, and thelower portion of the misaligned opening 230M may expose the first widthW₁ of the top surface of the second dielectric layer 178 as discussedabove. However, while the second dielectric layer 178 protects a topsurface of the first dielectric layer 174 as discussed above, an exposedside surface of the first dielectric layer 174 may be etched. As aresult of using an isotropic or anisotropic wet etch process, some ofthe wet etchants that reach the exposed side surface of the firstdielectric layer 174 may be able to etch laterally due to the low etchselectivity discussed above. For example, the first dielectric layer 174may be etched below the second dielectric layer 178 by a second widthW₂. As illustrated, the second dielectric layer 178 provides protectionto the first dielectric layer 174, and the first dielectric layer 174provides protection to the underlying IMD layer 110. Due to presence ofthe second dielectric layer 178, the etchant may etch only a smallportion of the first dielectric layer 174 below the second dielectriclayer 178. For example, the second width W₂ may be between about 0 Å andabout 50 Å.

In FIGS. 11A through 11C, a liner layer 240 (e.g., including one or morebarriers and one or more liners) is formed in the openings 230. Theliner layer 240 may be formed of similar materials and by a similarprocess, such as conformally deposited, as described above in connectionwith the liner layer 140.

In FIGS. 11B and 11C, zoomed-in views of region 236 (see FIG. 11A)illustrate varying shapes of the lower portions of one of the openings230, one of the misaligned openings 230M, and the liner layer 240. Forexample, the liner layer 240 may have a stair-step shape due to beingformed over and around the second dielectric layer 178. Referring toFIG. 11C, a portion of the liner layer 240 may fill the second width W₂adjacent to the first dielectric layer 174 and below the seconddielectric layer 178. In some embodiments, the liner layer 240 does notcompletely fill the second width W₂, and a void (not specificallyillustrated) may remain adjacent to the first dielectric layer 174 andbelow the second dielectric layer 178. The void may provide furtherinsulation to the structure without inhibiting electrical flow throughthe first conductive features 120 and the second conductive features220.

In FIGS. 12A through 12C, the second conductive features 220 arecompleted, for example, by filling the openings 230 with a conductivefill material 250, planarizing the conductive fill material 250 and theliner layer 240, and forming a capping layer 260 over the conductivefill material 250 and the liner layer 240. These processes may be formedusing similar materials and by similar methods as described above inconnection with the analogous features of the first conductive features120. In embodiments in which the void described above remains afterformation of the liner layer 240, the conductive fill material 250 mayfill the void or the void may still remain.

In FIGS. 12B and 12C, zoomed-in views of region 238 (see FIG. 12A)illustrate varying shapes of one of the second conductive features 220and one of the misaligned second conductive features 220M formed in themisaligned opening 230M. The misaligned second conductive feature 220Mmay comprise an overbite 220A and/or an underbite 220B. As discussedabove, in accordance with some embodiments, the misaligned secondconductive feature 220M may be located near one of the first conductivefeatures 120 (as illustrated) without being directly electricallyconnected to one another. In spite of the overbite 220A and/or theunderbite 220B causing the misaligned second conductive feature 220M tobe closer to the first conductive feature 120, the benefits of the firstdielectric layer 174 and the second dielectric layer 178 may berealized, as discussed below.

Referring to FIG. 12B, as discussed above, neighboring or adjacent onesof the first conductive features 120 may be separated from one anotherby the distance D₁. Without the presence of the first dielectric layer174 and the second dielectric layer 178, the misaligned secondconductive feature 220M would have an overbite that further extends downand to the side of the first conductive feature 120 to form atiger-tooth shape. For example, without the first and second dielectriclayers 174/178, the overbite portion of the misaligned second conductivefeature 220M would extend further down along a sidewall of the firstconductive feature 120 like the tooth of a saber-toothed tiger. As aresult, the tiger-tooth would cause the misaligned second conductivefeature 220M to be closer (than the distance D₁) to the nearby firstconductive feature 120 (e.g., the nearby one of the first conductivefeatures 120 that is not directly electrically connected to themisaligned second conductive feature 220M). Depending on how muchcloser, a parasitic capacitance could impede the performance of thecompleted integrated circuit device.

However, with the presence of the first dielectric layer 174 and thesecond dielectric layer 178, the overbite 220A described above andillustrated in the figures is formed (instead of the tiger-tooth) andremains a distance D₂ from the nearby first conductive feature 120. Thesecond distance D₂ may be about the same or less than the first distanceD₁. As a result, the overbite 220A of the misaligned second conductivefeature 220M will have minimal to zero contribution to causing parasiticcapacitance between the misaligned second conductive feature 220M andthe nearby first conductive feature 120.

Referring to FIG. 12C, with the presence of the first dielectric layer174 and the second dielectric layer 178, in addition to the overbite220A above the first dielectric layer 174, the underbite 220B may extendbelow a portion of the second dielectric layer 178. The underbite 220Bmay be a third distance D₃ from the nearby first conductive feature 120that is about the same or less than the first distance D₁ and/or thesecond distance D₂. As a result, the underbite 220B of the misalignedsecond conductive feature 220M will have minimal to zero contribution tocausing parasitic capacitance between the misaligned second conductivefeature 220M and the nearby first conductive feature 120. In someembodiments, the third distance D₃ is greater than the second distanceD₂ due to both the second dielectric layer 178 and the capping layer 160ensuring that only a small amount of etching occurs in the firstdielectric layer 174.

In FIGS. 13 through 17 , in accordance with some embodiments, thefront-side interconnect structure 80 is formed with a modification tothe above described process. Referring to FIG. 13 , before depositingthe capping layer 160, upper portions of the first conductive features120 (e.g., the conductive fill material 150) may be etched and recessedbelow a top surface of the liner layer 140 by between about 20 Å andabout 50 Å. Next, the capping layer 160 may be selectively depositedover the structure and into the recesses by one of the methods listedabove. In some embodiments, a top surface of the capping layer 160remains below top surfaces of the liner layer 140 and the IMD layer 110.

Referring to FIG. 14 , the blocking film 170 is selectively depositedover the capping layer 160, the first dielectric layer 174 isselectively deposited over the IMD layer 110, and the second dielectriclayer 178 is selectively deposited over the first dielectric layer 174,as described above. As illustrated, a top surface of the blocking film170 may be above the top surfaces of the liner layer 140 and the IMDlayer 110 while being below a top surface of the first dielectric layer174. Although not specifically illustrated, in some embodiments,portions of the blocking film 170 will also form over the liner layer140, thereby further preventing the first dielectric layer 174 and thesecond dielectric layer 178 from depositing directly on the liner layer140.

Referring to FIG. 15 , the blocking film 170 is removed, the etch stoplayer 208 is conformally deposited, and the IMD layer 210 is deposited,as described above. Referring to FIG. 16 , the IMD layer 210 and theetch stop layer 208 are etched to form the openings 230 (including themisaligned openings 230M), which will house the second conductivefeatures 220 (including the misaligned second conductive features 220M).As illustrated, the misaligned opening 230M may expose a first width W₁of the second dielectric layer 178. In some embodiments not illustratedhere, the second dielectric layer 178 may prevent the first dielectriclayer 174 from being etched. However, in some embodiments illustratedhere, a portion of the first dielectric layer 174 may be etched by athird width W₃ extending below the second dielectric layer 178. Thethird width W₃ may be less than first width W₁ due to protection fromthe overlying second dielectric layer 178, and greater than the secondwidth W₂ due to the capping layer 160 not being adjacent and proximalenough to protect the first dielectric layer 174 from etching. Forexample, the third width W₃ may be between about 0 Å and about 50 Å.

Referring to FIG. 16 , the liner layer 240 and the conductive fillmaterial 250 are formed in the openings 230 and planarized to removeexcess material as described above. As illustrated and described above,the resulting misaligned second conductive feature 220M formed in themisaligned opening 230M may comprise the overbite 220A and the underbite220B. Although not specifically illustrated, in other embodiments, theunderbite 220B is not formed because the first dielectric layer 174 mayremain substantially unetched.

As discussed above, nearby ones of the first conductive features 120 maybe separated from one another by the distance D₁. As such, the overbite220A of the misaligned second conductive feature 220M may be a fourthdistance D₄ from a nearby first conductive feature 120, and the fourthdistance D₄ may be less than the first distance D₁ and greater than thesecond distance D₂ due to the conductive fill material 150 beingrecessed before forming the capping layer 160. Further, the underbite220B of the misaligned second conductive feature 220M may be a fifthdistance D₅ from the nearby first conductive feature 120, and the fifthdistance D₅ may be less than the first distance D₁. In some embodiments,the fifth distance D₅ is less than the fourth distance D₄ due to thecapping layer 160 not being proximal enough to reduce the etching thatmay occur in the first dielectric layer 174.

Embodiments achieve various advantages. The first dielectric layer 174and the second dielectric layer 178 ensure that upper level conductivefeatures (e.g., the second conductive features 220) maintain enoughdistance from lower level conductive features (e.g., the firstconductive features 120) to prevent or reduce parasitic capacitance whenthe upper level conductive features are misaligned (e.g., the misalignedsecond conductive features 220M). As noted above, the low-k materialused in the first dielectric layer 174 ensures that parasiticcapacitance is prevented or reduced between all conductive features,whether first conductive features 120 or second conductive features220/220M and whether correctly aligned or misaligned. The blocking film170 ensures that the first dielectric layer 174 and the seconddielectric layer 178 are selectively formed over the IMD layers 110/210.As a result, during any misalignment of the upper conductive features,the second dielectric layer 178 prevents or minimizes etching of thefirst dielectric layer 174, which thereby prevents etching of theunderlying IMD layer 110. Further, in the cases of misalignments in thesecond conductive features 220M, the low-k material of the firstdielectric layer 174 minimizes any parasitic capacitance that wouldotherwise occur.

In an embodiment, a method includes forming a first conductive featurein a first inter-metal dielectric (IMD) layer; depositing a blockingfilm over and physically contacting the first conductive feature;depositing a first dielectric layer over and physically contacting thefirst IMD layer; depositing a second dielectric layer over andphysically contacting the first dielectric layer; removing the blockingfilm; depositing an etch stop layer over any physically contacting thefirst conductive feature and the second dielectric layer; forming asecond IMD layer over the etch stop layer; etching an opening in thesecond IMD layer and the etch stop layer to expose the first conductivefeature; and forming a second conductive feature in the opening. Inanother embodiment, the first dielectric layer is a low-k dielectricmaterial, and wherein the second dielectric layer is a high-k dielectricmaterial. In another embodiment, the etch stop layer and the seconddielectric layer comprise different etch selectivities. In anotherembodiment, depositing the blocking film comprises selectivelydepositing the blocking film over the first conductive feature. Inanother embodiment, removing the blocking film comprises selectivelyremoving the blocking film. In another embodiment, etching the openingfurther exposes a portion of the second dielectric layer. In anotherembodiment, during the etching the opening, an entirety of the first IMDlayer directly below the portion of the second dielectric layer remainsunetched. In another embodiment, during the etching the opening, thefirst dielectric layer is etched by a greater amount than the seconddielectric layer.

In an embodiment, a method includes forming a first conductive featureand a second conductive feature in a first dielectric layer; forming ablocking layer over the first conductive feature and the secondconductive feature; forming a multilayer dielectric over the firstdielectric layer and laterally displaced from the blocking layer, themultilayer dielectric comprising a low-k dielectric layer disposed overthe first dielectric layer and a high-k dielectric layer disposed overthe low-k dielectric layer; flowing a reacting gas to remove theblocking layer; depositing an etch stop layer over the high-k dielectriclayer; depositing a second dielectric layer over the etch stop layer;forming a trench in the second dielectric layer and the etch stop layer,the forming the trench comprising exposing the first conductive featureand the high-k dielectric layer; and forming a third conductive featurein the trench. In another embodiment, the forming the trench comprisesetching portions of the second dielectric layer, the etch stop layer,and the low-k dielectric layer. In another embodiment, the etch stoplayer and the high-k dielectric layer have a high etch selectivity. Inanother embodiment, the third conductive feature comprises a bulkportion extending to a top surface of the first conductive feature andan overbite portion extending to a top surface of the high-k dielectriclayer. In another embodiment, the first conductive feature is a firstdistance from the second conductive feature, wherein the thirdconductive feature is a second distance from the second conductivefeature, and wherein the second distance is less than the firstdistance. In another embodiment, the reacting gas comprises H₂ and/orNH₃. In another embodiment, the low-k dielectric layer comprises siliconoxide, and wherein the high-k dielectric layer comprises aluminum oxide.

In an embodiment, a device includes a first conductive feature and asecond conductive feature embedded in a first insulating layer, thefirst conductive feature being a first distance from the secondconductive feature; a low-k dielectric layer disposed over the firstinsulating layer; a high-k dielectric layer disposed over the low-kdielectric layer; a second insulating layer disposed over the high-kdielectric layer; and a third conductive feature embedded in the secondinsulating layer and physically contacting the first conductive feature,the high-k dielectric layer being directly interposed between a firstportion and a second portion of the third conductive feature, the firstportion of the third conductive feature being a second distance from thesecond conductive feature, the second distance being less than the firstdistance. In another embodiment, the second portion of the thirdconductive feature is a third distance from the second conductivefeature, the third distance being less than the first distance. Inanother embodiment, the second portion is interposed between the firstinsulating layer and the high-k dielectric layer. In another embodiment,the third conductive feature further physically contacts sidewalls ofthe low-k dielectric layer, the high-k dielectric layer, and the secondinsulating layer. In another embodiment, the third conductive featurefurther physically contacts a top surface of the high-k dielectriclayer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A device comprising: a first conductive featureand a second conductive feature embedded in a first insulating layer,the first conductive feature being a first distance from the secondconductive feature; a low-k dielectric layer disposed over the firstinsulating layer; a high-k dielectric layer disposed over the low-kdielectric layer; a second insulating layer disposed over the high-kdielectric layer; and a third conductive feature embedded in the secondinsulating layer and physically contacting the first conductive feature,the high-k dielectric layer being directly interposed between a firstportion and a second portion of the third conductive feature, the firstportion of the third conductive feature being a second distance from thesecond conductive feature, the second distance being less than the firstdistance.
 2. The device of claim 1, wherein the second portion of thethird conductive feature is a third distance from the second conductivefeature, the third distance being less than the first distance.
 3. Thedevice of claim 2, wherein the second portion is interposed between thefirst insulating layer and the high-k dielectric layer.
 4. The device ofclaim 1, wherein the third conductive feature further physicallycontacts sidewalls of the low-k dielectric layer, the high-k dielectriclayer, and the second insulating layer.
 5. The device of claim 4,wherein the third conductive feature further physically contacts a topsurface of the high-k dielectric layer.
 6. The device of claim 1,wherein the high-k dielectric layer being directly interposed betweenthe first portion and the second portion of the third conductive featurecomprises: the first portion being in physical contact with an uppersurface of the high-k dielectric layer; and the second portion being inphysical contact with a lower surface of the high-k dielectric layer,the lower surface being opposite to the upper surface.
 7. The device ofclaim 1, wherein the first conductive feature comprises a cobalt cappinglayer, and wherein a sidewall of the cobalt capping layer is in physicalcontact with a sidewall of the low-k dielectric layer.
 8. The device ofclaim 1, wherein the low-k dielectric layer comprises a first segmentextending between the third conductive feature and the second conductivefeature, wherein the high-k dielectric layer comprises a second segmentextending between the third conductive feature and the second conductivefeature, and wherein the first segment is shorter than the secondsegment.
 9. A device comprising: a first conductive feature embedded ina first inter-metal dielectric (IMD) layer; a low-k dielectric layerdisposed over the first IMD layer; a high-k dielectric layer disposedover the low-k dielectric layer; an etch stop layer disposed over andphysically contacting the first conductive feature and the high-kdielectric layer; a second IMD layer disposed over the etch stop layer;and a second conductive feature embedded in the second IMD layer andphysically contacting the first conductive feature, the high-kdielectric layer, the etch stop layer, and the second IMD layer.
 10. Thedevice of claim 9, wherein the second conductive feature furtherphysically contacts the low-k dielectric layer.
 11. The device of claim9, wherein the second conductive feature comprises an overbite portiondirectly above the high-k dielectric layer and the first IMD layer. 12.The device of claim 11, wherein the second conductive feature furthercomprises an underbite portion interposed between the high-k dielectriclayer and the first IMD layer.
 13. The device of claim 9 furthercomprising a third conductive feature embedded in the first IMD layerand laterally displaced from the first conductive feature.
 14. Thedevice of claim 13, wherein the third conductive feature is closer tothe second conductive feature than to the first conductive feature. 15.The device of claim 9, wherein the first conductive feature comprises acobalt capping layer, and wherein a sidewall of the cobalt capping layerphysically contacts a sidewall of the low-k dielectric layer.
 16. Adevice comprising: a first extra-low-k dielectric layer over asubstrate; a first conductive feature and a second conductive featureembedded in the first extra-low-k dielectric layer, the firstextra-low-k dielectric layer comprising a first segment extending fromthe first conductive feature to the second conductive feature; a low-kdielectric layer over the first extra-low-k dielectric layer, the low-kdielectric layer comprising a second segment extending along a topsurface of the first segment and between the first conductive featureand the second conductive feature; a high-k dielectric layer over thelow-k dielectric layer, the high-k dielectric layer comprising a thirdsegment extending along a top surface of the second segment and betweenthe first conductive feature and the second conductive feature; an etchstop layer over the high-k dielectric layer, the etch stop layercomprising a fourth segment extending along a top surface of the thirdsegment, a sidewall of the third segment, and a sidewall of the secondsegment; a second extra-low-k dielectric layer over the high-kdielectric layer; and a third conductive feature embedded in the secondextra-low-k dielectric layer and in physical contact with the firstconductive feature.
 17. The device of claim 16, wherein the fourthsegment of the etch stop layer is in physical contact with the thirdconductive feature and the second conductive feature.
 18. The device ofclaim 16, wherein the third segment is longer than the second segment.19. The device of claim 16, wherein the third conductive featurecomprises a first portion in physical contact with the second segmentand the third segment, and wherein the first portion is directlyinterposed between the second segment and the third segment.
 20. Thedevice of claim 19, wherein the first portion of the third conductivefeature is closer to the second conductive feature than the firstconductive feature is to the second conductive feature.